Mitsubishi Electric MELSEC iQ-F FX5 - Page 659

35 CPU MODULE BUILT-IN ANALOG FUNCTION
35.6 Function (PID Control Via Parameter)
657
35
Output limiter function
The output limiter is a function that sets the upper and lower limit values if outputting the output value (MV) calculated using
PID operations to an external device.
It is disabled only when executing two-position control.
Output change ratio limiter function
The output change ratio limiter is a function that limits the amount of change in the output value (MV) per unit time (1s).
Control outputs are limited using the output change rate that has been set.
For a control target that goes out of control due to a sudden change in the output or a control target in which a large current
flows, setting the output variation limiter is effective.
When the target value (SV) is changed, the output value (MV) does not change suddenly, and outputs are made based on the
set gradient. When the set value is 0, this function is disabled.
The output value (MV) limited by the output change ratio limiter function can be obtained by the following formula.
Output value (MV) = (Previous output value (MV)  Output change ratio limiter (%)  (Sampling time (ms)  1000)
■When the output change ratio limiter is effective
The output change ratio limiter is effective in the following cases.
• If the output value (MV) starts from 100% at the start of control (When there is a problem with a 100% sudden change)
• If the output value (MV) changes suddenly due to a change in the target value (SV)
Ex.
When the rise of the output change ratio limiter is effective
When the target value (SV) is changed significantly, the output does not change suddenly, and outputs are made based on the
set gradient.
■Precautions
• Reducing the output change ratio limiter value (reducing the gradient) slows the control response. In addition, the effect of
differentiation is lost.
• The output change rate limiter is disabled when executing two-position control.
100%
0%
Output value (MV)
This range has no control outputs.
Upper limit output limiter
Lower limit output limiter
This range has no control outputs.
When the output change rate limiter is not set
Upper limit output limiter
Output value (MV)
0.1 to 100.0%
1 second
Sudden change
of output value
Set how much (%) the output value
should change in one second.
Output value (MV)
Lower limit output limiter
Sudden output change due to a shift to operation mode, a change of target value (SV),
or disturbance